1. Field of the Invention
The present invention relates generally to any turbomachinery equipment with "axial entry" blades. More specifically, the present invention relates to steam turbines of the type employing "axial entry" blades. The invention has particular application to steam turbines of the type wherein the blades have a generally fir tree shaped root in registration with a generally fir tree shaped groove.
2. Description of the Prior Art
Steam turbines of the type employing "axial entry" blades are known. In such turbines, the disc (i.e., the portion of the rotor that holds the blades) has a plurality of generally fir tree shaped, generally axially extending grooves disposed therearound. A plurality of blades are circularly disposed around the disc. Each blade has a generally fir tree shaped root in registration with one of the grooves.
A problem with such turbines is that windage losses may be created by misalignment between the faces of the root and the disc. Misalignment may also be present between adjacent blade platforms, also adding to windage losses. Further, a small clearance often exists between each root and the edges of the groove with which it registers, as well as between and under the blade platforms, which provides a leakage path for steam. These conditions are undesirable.